The invention relates to a hydroformylation process wherein ethylenically unsaturated compounds are contacted with carbon monoxide and hydrogen gas in a reaction zone in the presence of a solvent and a homogeneous catalyst based on a Group 8, 9 or 10 metal (referring to the IUPAC classification of elements in use in 1997).
The hydroformylation of ethylenically unsaturated compounds, to form products such as aldehydes and/or alcohols, is of considerable industrial importance. As is apparent from the literature, e.g., "New Syntheses with Carbon Monoxide" by J. Falbe (Springer-Verlag 1980; ISBN 0-387-09674-4) and "Carbonylation" by H. M. Colqhoun, D. J. Thompson and M. V. Twigg (Plenum Press 1991; ISBN 0-306-43747-3) a multitude of catalysts based on Group 8, 9 or 10 metals (Fe, Ru, Os; Co, Rh, Ir; Ni, Pd, and Pt) have been used in hydro-formylation processes. The most important industrial hydroformylation processes are presently based on the Group 9 metals; Co and Rh. Extensive patent art is also present on hydroformylation processes based on the Group 10 metals, Ni, Pd and Pt.
For various reasons, not in the least the costs of replacing lost catalyst, the catalyst must be recovered from the hydroformylation product. Mere distillation of the hydroformylation product, however, may inactivate and hence destroy the catalyst. Catalysts that are prone to destruction are therefore separated, for instance, by extraction.
In International application WO 95/05354 a process is disclosed wherein a major portion of the metal component of the catalyst system is recovered by causing at the end of the reaction the crude product to form two immiscible layers, and separating the layer comprising the hydroformylation product from the layer comprising the catalyst. The product layer, however, will still contain active catalyst. This reference provides no teaching how that should be recovered.
From EP-A-0,350,922 a process is known for the separation and recovery of an aldehyde product from a non-aqueous hydroformylation reaction product composition. The process involves phase separation using added water or both added water and an added non-polar hydrocarbon compound. Comparative example 1 of this reference illustrates the inadequacy of recovery by mere phase separation, whilst improved phase separation is shown when water is added. However, it should be observed that this process is conducted in the presence of a water soluble hydroformylation catalyst system. Thus, ionically charged phosphorus ligands are used, which will together with the metal complex- easily separate into the aqueous phase during the phase separation step. For catalyst systems based on non-ionically charged phosphorus ligands, which are the more common type ligands, this document provides no teaching either.
The inventors have set out to develop a hydro-formylation process, based on non-ionically charged ligands, with essentially full catalyst recovery.